There are many known systems which operate in conjunction with the braking system of a vehicle to prevent skidding or excessive deceleration. Particularly, the aircraft industry has found a keen need for such systems, to allow the aircraft to attain maximum braking effort, consistent with passenger comfort and safety, while reducing wear on the aircraft tires and obtaining shorter distance stops than previously known. These antiskid control systems allow the braking effort of the aircraft to approach a skidding situation, but release brake pressure prior to or at the skid since braking efficiency drops off drastically in a skidding situation.
Early antiskid systems were of the "bang-bang" or "on/off" type in which the antiskid brake valve was either fully opened or fully closed, there being no metering of such valve. Such systems were of a rudimentary nature, allowing for some increase in braking efficiency over the previously known art, but failing to approach optimization.
Present day antiskid control systems obtain a high degree of control, providing for proportional, integral, and derivative control, but do so with systems which are often complex, expensive, and of undesirable weight for utilization in an aircraft. The sophistication of presently known systems makes them unsuited for many aircraft applications.
Presently needed in the aircraft industry is a simple, lightweight, inexpensive, and reliable antiskid system which can achieve accurate metering of brake pressure in response to wheel speed signals. Further, it is most desirable that in such a system the benefits of reduced cost, weight, and maintenance, and the increased reliability of the system more than compensate for any reduction in performance experienced over the more complicated prior art systems.